The present invention relates to devices for affixing a filter mesh to the drum of a rotary vacuum drum filter, and in particular to such devices employing foraminous support elements for carrying the filter mesh which extend in the axial direction along the outside wall of the drum and which are uniformly distributed over the drum circumference.
Means for affixing a filter mesh to the exterior of the drum of a rotary drum filter are known in the art which utilize a number of foraminous support elements which are uniformly spaced around the circumference of the drum and which extend in the axial direction of the drum. The support elements form individual cells between the exterior wall of the drum and the filter mesh and at least one filter mesh clamping element is provided between adjacent support elements. In order to hold the filter mesh in place on the support elements, a fitting strip, which has a wedge-like cross section, is employed as a clamping element. The nearest sides of adjacent support elements form a corresponding wedge for receiving the fitting strip and the fitting strip is thus pressed into this wedge with the filter mesh between the fitting strip and the support elements, thereby holding the filter mesh in place. The filter mesh is greatly deformed at those clamping locations.
Because of the extreme deformation of the filter mesh which results from the above-described conventional filter affixing means, such known means can only be employed with a filter mesh consisting of fabric or some other highly elastic thin material, but cannot be employed with a filter mesh consisting of a metal wire web, as is generally employed for vacuum drum filters.
An attempted solution to employ the known affixing means to a metallic filter mesh, the metallic filter mesh has been cut into individual segments having a width which corresponds to the width of the support elements between the clamping elements so that the metallic mesh extends only partially into the wedge between such supporting elements. Because a separate filter mesh segment is thus required for each support element and a separate fitting strip is required between every two adjacent support elements, this attempted solution for affixing a metallic filter mesh to the drum of a rotary drum filter results in a significantly higher material and assembly time outlay.
It is an object of the present invention to provide a device for affixing a metallic filter mesh to the exterior wall of a rotary drum filter which is economical to assemble and which results in minimal deformation of the metallic filter mesh.
This object is inventively achieved in a device for affixing a metallic filter mesh to the drum of a rotary vacuum drum filter wherein a plurality of spacer elements are respectively disposed between adjacent support elements and are attached to the exterior wall of the drum, and an axially extending strip is disposed over the spacer elements with the metallic mesh disposed therebetween, and the strips are respectively attached to the corresponding spacer elements, thereby affixing the mesh along the surfaces of the supporting elements. The spacer element has approximately the same height as the adjacent support elements, so that the filter mesh can be trained about the exterior surfaces of the support elements and rigidly clamped thereto by means of the axial strips without creasing or substantially deforming the filter mesh. The filter mesh can thus be a relatively stiff metallic mesh and can be trained about the filter drum in one piece.
The support elements have a widened U-shaped cross section so as to form individual cells beneath each support element. In a further embodiment of the invention, the clamping elements alternate between adjacent support elements with a sealing strip which is disposed between two support elements so as to seal the cells formed by each support element.
In a further embodiment of the invention, a support mesh, which is also held in place by means of the clamping elements disposed between adjacent support elements, is disposed between the support elements and the filter mesh. The presence of the support mesh between the support elements and the filter mesh greatly improves the filtration effect of the overall structure.
In another embodiment of the invention the end walls of the support elements are terminated by means of sealing rings. This results in a reliable seal of the cells formed by the support elements as well as sealing the end of the entire filter drum in a relatively simple manner.